If we take a 31 x 41 camera with a f.6.3 anastigmat lens and make a photograph with lens wide open and the distance set for 50 feet, objects from 29 feet to a distance of 170 feet should be sharp. If we make a duplicate photograph, stopping the lens to f.16, objects from 18 feet to infinity, or far as the view extends, should be sharp. Any other 5 lens, whether meniscus or rectilinear with stop f.16 will give exactly the same amount of depth and the exposure for all of these lenses will be the same. If, then, we wish to take advantage of the so-called speed of the anastigmat lens, we can only do so by opening up the stops to let in more light and thereby sacrifice the depth of focus in the picture. Fig. 15 shows the relative sized stops of a 5 inch lens, with the required exposures and the depth of focus with each stop when the camera is set for 50 feet,

To the average worker, the principal advantage of the anas

Camera set for 50 feet tallo dans

Figure 15. Relative size of the diaphram opening of a 54 inch lens with the relative exposures and depth of field with the camera set for fifty feet.

tigmat lens over the rectilinear are the flat field which insures negatives sharp to the edges even when used wide open, and the larger apertures which allow for shorter exposures under unfavorable conditions, although some of the depth must be sacrificed. In general these lenses should be used just the same as a rectilinear.

The loss in the depth of focus with large apertures is more apparent in longer focus lenses such as are used on 5 x 7 to 8 x 10 cameras. This is one advantage in using a small camera for field work. With care in focusing or in using the focusing scale for the principal objects, reasonably sharp negatives can be made with lenses up to the 31 x 4 size when used wide open. Unless actually cloudy, this will allow exposures of one-hundredth of as second at f.6.3 when photographing spraying operations and similar operations that require a short exposure in order that the movement does not blur the picture..

For photographing insects and their work in the laboratory, it is necessary to have a larger camera with a long bellows. While there are a number of cameras designed for photo-micrograph work, there is no camera on the market that is entirely satisfactory for photographing insects from natural size up to eight or 10 diameters. In our work, we use a 5 x 7 view camera mounted on a stand that allows the camera to be used either in a vertical or horizontal position.

A lens of about four inch focus is used in photographing insects natural size or twice natural size. This requires a bellows extension of twice the focal length for natural size and three times for twice natural size, or eight and 12 inches respectively. In photographing insect eggs or similar small objects, it may be necessary to make the direct photograph six to 10 times natural size. To do this with the four inch lens, it would require a bellows length of 44 inches for the 10 times enlargement; as the camera has only a 22 inch bellows, we use lenses such as are used on motion picture cameras with focal length of only one and onehalf or two inches.

The question naturally occurs, how can we use these small lenses designed to use on a film only a little larger than a postage stamp to cover a 5 x 7 plate. We are simply converting the short focus lens into a long focus lens and bringing the object to photograph very near to the lens. As soon as we do this, the values of the stops in the lens are changed in relation to the focal length and the exposure has to be greatly increased in proportion to the given enlargement. If the exposure for natural size is expressed as 1, the increase in exposure for various sized enlargements is as follows:

We are using cut films instead of glass plates in most of our work. Regardless of the argument that the films do not lie flat and are inferior to plates, I feel that we are getting equally good results with the films and they have a number of advantages over the plates. Halation is reduced to a minimum and there is no danger of breakage. They are much lighter in weight and about 25 can be stored in the same space as a dozen plates. Panchromatic films with a set of color screens to be used with them are desirable to bring out colors that will not show contrast on regular or even Orthochromatic films.

In photographing insects or their work in the laboratory, the material is placed on a piece of ground glass with the background two or three inches below to eliminate the shadows. From an artistic standpoint shadows may add to the photograph, but they often detract from and add confusion to scientific photographs which should be as simple and clean cut as possible. The back

ground is usually a piece of white cardboard, although various tints of gray are used to bring out contrast with light-colored or white objects. Pieces of white cardboard are also set up for reflectors to light the shaded side of the object.

The chief requisite in photographing caterpillars is patience. As a rule the specimens will appear natural only when photographed alive. Better results can be obtained with one to three specimens than where more are included. When possible the specimens should be placed on some of the food plant which shows characteristic work of the species. The food plant must lie as flat as possible, and twigs or leaves out of the general plane should be removed as they will be out of focus in the photograph. Most of the caterpillar photographs are made natural size as enlarging them would require too long an exposure. The lens should be stopped down as much as possible, depending upon the activity of the insects. As we use daylight for most of the exposures, it requires from five to 10 seconds with f.8 stop; more often a smaller stop is used. With the specimens focused and the cap over the lens, the slide is drawn from the plate holder. It is then a case of watching and waiting for the specimens to become still for the required exposure.

Slightly pinching a caterpillar or tapping it with a pencil will sometimes cause it to remain quiet. In some cases it is necessary to stupify the specimens with chloroform but this should only be done when they will remain quiet in no other way.

There are many occasions to make illustrations of adult insects from dead specimens. Though there has been some controversy as to whether the specimens appear more natural to the average person if symmetrically set or photographed without such preparation, in either case a specimen will not appear as in nature and the writer feels that an illustration of an insect is more satisfactory if it shows all six legs than when it gives the impression of having but one or two.

It is often desirable to show butterflies and moths with the wings folded in a resting position. Large specimens can often be photographed alive in a characteristic resting position. Where we wish to show the wing-spread and especially the under wings, carefully set specimens make much better photographs than those set in a careless manner. Pinned specimens are usually set in a piece of cork covered with white paper. Where possible it is well to cut off the head and portion of the pin above the insect close to the body.

In making enlarged photographs of small insects, it is often difficult to focus the object due to a certain amount of play in the camera adjustments. To overcome this an ordinary dissecting microscope has been fitted with a glass object carrier on the lens arm. The object to be photographed is placed on this, the camera bellows set for the right magnification and the object

brought into the focal plane by using the rack and pinion of the dissecting stand.

The exposures in insect photography should be fully timed. If the detail is present in the negative, sufficient contrast can often be obtained with the proper grade of photographic papers. Satisfactory prints, however, cannot be made from under-exposed negatives; if the detail is lacking there is no way to supply it and if possible another negative should be made.

Good insect photographs after all depend largely upon the experience of the operator and his ability to use the available apparatus and materials to the best advantage.

MOSQUITO CONTROL WORK IN CONNECTICUT. Season of 1924.

R. C. BOTSFORD.

The Director of the Connecticut Agricultural Experiment Station is charged by Statute with the maintenance of drainage works for mosquito elimination, inspected and approved by him. He may also upon request inspect and survey mosquito breeding areas, furnish estimates of cost of treating these areas and supervise or regulate the work. The area of 5,000 acres of ditched salt marsh under State maintenance and contained in nine shore towns was patrolled from April 1 until October 1. Ditches were kept free from obstructions and when found in bad condition, were recut and graded as far as funds would permit. About 155,000 lineal feet were recut. As a result there were but few spots where salt marsh pools would have remained long enough to develop adult mosquitoes. In such cases, oil was sprayed on the pools at the proper time.

The inland or fresh water work is at present limited to making investigations of mosquito infested areas upon request. In such instances, practical advice is given concerning the elimination of each particular breeding place.

Mosquito control work has been generally successful this season and there has been a notable increase of interest shown throughout the State in the mosquito problem.

The expenditures for the year 1924 were as follows:

New work and maintenance work supervised by the State where funds were provided by individuals, associations or towns:

The following table shows the present condition of the salt marsh areas in the coast towns. It was prepared from data immediately available and is subject to correction.

Totals.... 17,636 6,440 5,190 $57,017.61 $5,019.95 $147,500.00

THE WORK BY TOWNS.

NEW HAVEN.

The town of New Haven contains about 750 acres of salt marsh, all of which was ditched for mosquito elimination during the period from 1912-1917. These salt marsh areas were patrolled continuously from April 1 to October 1, and about 20,500 lineal feet of ditches found in bad condition were recut and graded. Some breeding was discovered where drainage was not yet perfect, but oil was sprayed on the water at the proper time to prevent emergence. There was practically no emergence of mosquitoes from the salt marshes in the town of New Haven in 1924. In spite of this fact, New Haven was more or less infested with salt marsh mosquitoes throughout the summer. This was